A model based method is often used for estimating a position of a target object in images with limited resolution in, for example, microscopic images or telescope images whose resolution is limited by optics such as diffraction limit. In model based method, the target object, such as a light emitting particle, is modeled as, for example, a spot in a certain shape in the image, at an assumed size and brightness. Then the optimization of the model over the observed light emitting particles is carried out to calculate a probability of the assumed model.
Patent Literature PTL 1 discloses a mark detection device which detects a mark by using models each having a small difference in shape among them.